Emission control: 80 percent lower nitrogen oxide emissions with SCR technology

The matter of exhaust emissions was a further important task for the developers of the concept car. While the up-to-date CDI engine already betters the stringent EU 4 exhaust emission limits significantly thanks to an oxidising catalytic converter and a particulate filter, the engineers in Stuttgart have an eye to the future and are testing an innovative process which promises to meet even more exacting standards in the future, namely SCR technology (Selective Catalytic Reduction).

The centrepiece is a catalytic converter which uses an additional service fluid to convert the nitrogen oxides (NOx): an aqueous urea solution is sprayed into the exhaust system in precisely metered quantities, depending on the engine operating status. This converts the nitrogen oxides into harmless nitrogen and water. The result is an up to 80 percent reduction in NOx emissions in the new European driving cycle.

DaimlerChrysler is currently testing its SCR technology worldwide. By this means, and with the additional operating fluid "AdBlue", the nitrogen oxide emissions of the direct-injection diesel engine can be reduced by up to 80 percent. The aim of these trials is to avoid the fuel consumption disadvantages by optimising the in-engine combustion processes. This is where Mercedes-Benz car engineers are benefiting from the experience gained by their colleagues in the commercial vehicle sector, where SCR technology is already in successful use. DaimlerChrysler also intends to use the great potential of this process for diesel passenger cars in future, and initially intends to offer SCR technology in the USA when the trials have been completed.

The service fluid which allows selective catalytic combustion is named "AdBlue". As only very small quantities are required when on the move, the capacity of the reservoir located in the spare wheel recess of the concept car is sufficient for a mileage corresponding to the service interval for a current Mercedes diesel car.